Ocean exploration has been conducted in order to search resources present on the seabed, such as petroleum, natural gas, gas hydrate, and the like.
Generally, in an ocean exploration method, exploration of predicting whether or not submarine resources such as petroleum, natural gas, gas hydrate, and the like, are present using a seismic exploration method, an unmanned underwater vehicle, or the like, is preferentially performed.
The seismic exploration method is a method based on a feature that an interval velocity of a seismic wave in pure gas hydrate is faster than that of a seismic wave in a sedimentary layer, such that an interval velocity of the seismic wave in a sedimentary layer containing gas hydrate is faster than that of the seismic wave in a sedimentary layer not containing gas hydrate and a feature that a seismic chimney, or the like, is shown in a cross-sectional view of the seismic wave and gas hydrate, or the like, is present at an upper portion of the seismic chimney.
The exploration method using the unmanned underwater vehicle is a method for exploring whether or not the gas hydrate is present by measuring concentrations of methane gas through injection of an exploration apparatus into the seabed since the methane gas is discharged in the case in which the gas hydrate is present on the seabed.
Korean Patent No. 10-1048528 has suggested an exploration method using an unmanned underwater vehicle.
When it is determined by the seismic exploration method and the exploration method using an unmanned underwater vehicle as described above that the submarine resource such as gas hydrate, or the like is present, a drilling apparatus descends to a submarine surface of a corresponding point to perform drilling, thereby directly confirming whether or not the submarine resource is present.
Korean Patent No. 10-0978143 has suggested a structure of an apparatus for drilling submarine sediment.
Meanwhile, the gas hydrate, which is a new clean energy source of the 21 century capable of substituting fossil fuels and an energy source formed by being combined with water in a low temperature and high pressure state of the permafrost or the deep sea, has an appearance similar to that of dry ice and has a property that it may be burned with fire, such that it is also called burning ice (a main component of the gas hydrate is methane gas).
However, since most of the gas hydrate is positioned at the deep sea, a significantly long time is required to obtain drilled gas hydrate in a state in which it is filled in a core in gas hydrate exploration onto a ship. In addition, when the gas hydrate is obtained onto the ship in a state in which it is changed in a low temperature and high pressure environment to a room temperature and normal pressure environment, the gas hydrate is in a state in which it is significantly dissociated or completely dissociated.
According to the related art, after the gas hydrate drilled in a state in which it is filled in the core is put in liquid nitrogen and moved to a laboratory on land, an analysis experiment for examining whether or not the gas hydrate is present has been conducted.
Therefore, an original form or component is contaminated during a process of moving the gas hydrate obtained onto the ship to the laboratory on land, such that it is difficult to secure accuracy of the analysis experiment (the gas hydrate is completely dissociated generally in one hour).
As a result, reliability of judgment of whether or not the gas hydrate is present has been decreased.